Photo-Electron guns require vacuum at the lowest
limits of the Ultra-High Vacuum (UHV) range, below 1x10-11Torr, in order to maximize quantum efficiency and
cathode lifetime. The vacuum levels required for the electron
gun exceed the requirements of any other portion of the CEBAF accelerator.

Extensive research has been performed within the Electron Gun Group to
produce this UHV environment. This research includes: